Our preliminary work with the Wiesel-Raviola lid-suture myopia model in the Rhesus monkey suggests that the refractive state of highly hyperopic eyes may not change in response to lid-suture. Highly hyperopic monkeys are extremely rare, but we have been successful in producing high hyperopia in one infant monkey by dark-rearing. We plan to confirm these results by dark-rearing five Rhesus monkeys and using atropine in at least half the eyes to stabilize the hyperopia which results. Refractive state and ocular dimensions will be monitored at 2-week intervals by cycloplegic retinoscopy and A-scan ultrasonography, respectively. Monocular lid suture will be performed at 10 weeks of age for bilaterally hyperopic monkeys, with refractive state and ocular dimensions being monitored upon opening the lids at 6-month intervals. By exploring this possible model for hyperopia, we hope to open a new pathway to understanding the mechanisms for myopia development, particularly the elusive mechanism involved in the lid-suture myopia model. Our preliminary data for the hyperopia model must be strengthened and confirmed before proceeding with the larger task of dissecting out the particular stimuli and variables involved. With increasing evidence for environmental influence upon the refractive state of the eye, critical research in this area has the potential for sound clinical application. We are combining our optical, clinical, and bioengineering skills in an attempt to meet this goal.